Process for the production of hydroaromatic hydrocarbons



Patented Oct. 20,

: PBOCESS'FOR THE PRODUCTION OF HY- DROABOMATIC HYDROCARBONS I V AdrlanusjJohannes van Peski,

erlands, assignor to Shell ,pany, San Francisco, Calif a corporation of Delaware I Amsterdam, Neth- Development Com- No Drawing. Application May 11, 1940, Serial The present invention relates to a process for the production of hydroaromatic hydrocarbons such as cyclohexane and itsalkyl derivatives from naphthenic distillates. 1

Hydroaromatic hydrocarbons such as cyclohexane and its lower alkyl derivatives, being excellent starting materials for the synthesis of a host of, chemicals such hexanone, adipic acid,

etc., are very valuable materials.

At present, practically the entire sup,-

ply of these hydrocarbons must be produced from coal tar distillates by hydrogenation, and since the coal tar distillates are available only in limited quantities, these various hydroaromatic hydrocarbons are quite expensive.

It is known that there exist various hydrocarbon fractions of complicated composition which contain appreciable andeven predominant proportions of naphthenic hydrocarbons. Such fractions, referred to generally as naphthenic fractions or stocks, are available from various sources such as from naphthenic petroleums, the destructive hydrogenation of coal and other carbonaceous material, certain extracts obtained in hydrocarbon treating processes, etc. These distillates contain naphthenic hydrocarbons of two types, namely hydroaromatic naphthenes (i. e., having six-membered rings) and non-hydroaromatic naphthenes (i. e., having other than six-membered rings); Examples or hydroaromatic naphthenes are cyclohexane and its alkylated derivatives. ,Examples of non-hydroaromatic naphthenes are cyclobutane, cyclopentane, cycloheptane, and their variousalkylated derivatives. The naphthenic hydrocarbons present in commercial naphthenic distillates' nearly always consist almost entirely of those having 5- and 6- membered rings, and these two main types of naphthenic hydrocarbons are "usually present I in about equal proportions. Due, however, to the complexity of these distillates, it has hitherto been impossible to separate and recover hydroaromatic hydrocarbons from such naphthenic distillates in a practical manner. I

I have invented a process whereby hydroaromatic hydrocarbons of almost any desired degree of purity maybe produced a practical and economical manner from various naphthenic distillates. In the process of my invention I make use of certainisomerization reactions and the changes in the boiling points of the various hydrocarbon constituents induced thereby.

In its broader aspect, the process of the invention comprises three steps, namely, from a naphthenic hydrocarbon stock separating as cyciohexanol, cyclois, I believe, beneficial fractional distillation In the Netherlands September 8 Claims. (014260-666)- containing naphthenic hydrocarbons oi the desired number of carbon atoms, subjecting said fraction to an isomerization treatment to convert non-hydroaromatic naphthenes to hydroaromatic hydrocarbons, and fractionating the thus treated distillate to recover hydroaromatic,

hydrocarbons.

As stated above, due to the complexity of the naphthenic distillates, it has hitherto been impossible to separate hydroaromatic hydrocarbons from these distillates by commercial fracir a naphthenic distillate of suitable boiling range is first subjected to an isomerization treatment and then refractionated, it is possible to recover substantial quantities of hydroaromatic hydrocarbons in almost any desired purity from such distillates. The isomerization treatment in two ways. One efiect of the isomerization treatment is to convert nonhydroaromatic naphthenes into their higher boiling hydroaromatic isomers. Thus, for example, 1,1 dimethyl cyclopentane (B. P. 88 0.), is converted largely into methyl cyclohexane (B. P. 101 C.) Another eflect or the isomeriza tion treatment is to convert normal and slightly branched paraflin hydrocarbons present into branched and which have lowerboiling points. Thus, for example, n-heptane (B. P. 98 1 C.) is converted to Z-methyl hexane (B. P. 90 C.) and 3-methyl hexane (B P. 92 C.). The overall efiect, or the isomerization treatment is therefore firstly to increase the concentration of hydroaromatic hydrocarbons by, isomerization of non-hydroaroniatic naphthenes, secondly, to decrease the com plexity of the hydrocarbon mixture to a certain extent by decreasing the concentration of nonhydroaromatic hydrocarbons which make the separation of hydroaromatic hydrocarbons by more diillcult, and thirdly, to increase the diiiferences in boiling points between the desired hydroaromatic hydrocarbons a fraction 3 to choose or separate a naphthenic It is desired to and the other non-cyclichydrocarbon constituents of the mixture.

In the practice of my invention it is necessary distillate boilmg approximately to, but not above, the boiling point or the hydroaromatic hydrocarbons, .or mixture of hydroaromatichydrocarbons, which if it is desired a naphthenic traction boiling up advantageously employed. If,

on the other hand, it is desired to produce cyclo-,

tionation methods. I have found, however, that more highly branched isomers hexane, a lower boiling naphthenic fraction, for instance, boiling up to about 75-78" C., is employed, or if it is desired to produce higher boiling hydroaromatics a correspondingly higher boiling naphthenic fraction, for instance bolting to about 150 C. is used. It is preferable that the naphthenic distillate be free of substantial amounts of olefinic hydrocarbons. Olefinic hydrocarbons, if present in substantial quantities impair the efiiciency of the process since, under the influence of aluminum chloride and similar catalyst, they tend to polymerize and undergo other reactions which produce undesirable higher boiling materials that tend to contaminate the product. Aromatic-hydrocarbons, if present in substantial quantities tend to form azeotropic mixtures with the hydroaromatic hydrocarbons temperatures, may be repressed by the use of hydrogen pressure according to the method described in copending application, Serial No.

323,409, filed March '11, 1940. Advantageous methods of executing the isomerization are i'ure ther described incopending application, Serial and decrease the efliciency of the subsequent fractionation. It it is desired to obtain the highest yield of substantially pure hydroaromatic hydrocarbons, it is, therefore, preferable to employ substantially aromatic-free distillates. If the stock to be treated contains appreciable quantities of olefinic or aromatic hydrocarbons, these may be removed or reduced to unobjectionable concentrations by any of the conventional means, such, for instance, as selective solvent extraction, hydrogenation, acid treatment, etc.

The isomerization of the naphthenic fraction may be effected by heating the distillate at a suitable temperature with an isomerization catalyst. The catalysts preferably employed are anhydrous AlCla and AlBrz. Of'these MCI: is preferred since it is less expensive, easier to employ, and has a lesser tendency than AlBra to cause degradation of naphthenic hydrocarbons. Other acid-acting metal halide catalysts which may be employed if desired in conjunction with AlCls or AlBra, are the halides of T1, Ga, Zr, Ta, Nb, In, B and the like.

Aluminum chloride, if this catalyst is used, may be employed in any one of several ways. Thus, for example, it may be simply suspended in the reaction mixture (for this method of operation the process described in copending application Serial No. 298,594, filed October 9, 1939, may be advantageously employed) or it may be impregnated in an adsorptive carrier material and contacted in this form with the hydrocarbon; or. it may be employed, as a complex AlCla-hYdl'OCflI- 'bon double compound such, for instance, as a Gustavson complex of the general formula MC13.C6HnR6-n wherein R stands for an alkyl radical (very suitable complex catalysts may be prepared by heating kerosene with AlBr: and/or A1C13); or it may be used in combination with No. 323,410, filed March 11, 1940.

The naphthenic fraction after being subjected to an isomerization treatment is fractionally'distilled to recover hydroaromatic hydrocarbons. Thus, after fractionally distilling the isomerized fraction until all material boiling within the boiling range of the fraction before isomerization' has been removed, a residue'is left which consists essentially of hydroaromatic hydrocarbons. These may be recovered substantially pure in most cases by simply'continuing the distillation and collecting the distillate in one ormore sepa-,

rate containers. I

The following example which describesthe production of a hydroaromatic hydrocarbon from'a commercial naphthenic stock and is comprised within the scope of the invention is given to show the advantages and practicability of 'the-invention and is not intended to impose undue limita-,-.

matic naphthenes B0 Aromatic hydrocarbons 10 Parailinic hydrocarbons 30 (The presence of aromatic hydrocarbons in this I fraction is due to the difliculty of eflectin'g a clean separation by the fractionation of such complicated hydrocarbon mixtures and due to the fact that certain aromatic hydrocarbons form azeotropic mixtures with naphthenic hydrocar This highly naphthenic fraction was bons.) isomerized by treating it with 1% by weight of anhydrous aluminum chloride and 5% by weight of hydrogen chloride at 80 C; for 10 hours.

- After decantation from the catalyst, washing and drying, the product was subjected to fractional salts'of other'metals, such as the halides of Be, Sb, Zn, Sn, Co, Cu, etc. The AlCla-hydrocarbon complex catalysts are especially advantageous for use in the-present, process since they tend to produce lesser amounts'of higher boiling products;

which may contaminate the product.

When the isomerization is effected. with an acid-acting metal halide catalyst, it is'preferable that at least a trace of a free hydrogenhalide (HCl, HBr, HI or HF), be present to act as a promoter. In general, the activity of the catalyst is more or less proportional to the promoter con centration. While only very'small amounts of hydrogen halide are sufficient to promote the activity of the catalyst, much better resultsmay, in general, be obtained by theuse of partial pressures of hydrogen halide at least equal to 1 and preferably 3-20 atmospheres.

In general, the isomerization treatment is exedistillation. 55% by weight of a fraction boiling between 55 C. and 78 C. and 45% by weight of a fraction boiling between 78 C. and 80.5? C.

were obtained. The latterfraction had an index:

and consisted substa'n I of refractionof 1.4265- tially of cyclohexane.

- When the reaction product from the isomeriza's;

tion treatment'was first treated at 20 C. with-3 parts by weight of 98% sulfuric acid toremove aromatic hydrocarbons and then subjected to the fractionation as before, 50% by weight. I (calculated on the reaction product) of a free-1 tion boiling between 78 C. and 80.5 C. was ob-',

tained. This material was substantially pure,

cyclohexane.

While I have described my invention in its preferred embodiment and given a specific example illustrating its use, I am aware that various changes and modifications will be apparent to those skilled in the art. It is my intention,

from naphthenic distillates which comprises the steps of separating from a naphthenic distillate by fractional distillation a fraction boiling up to about 75-78 C. and containing paraflin hydrocarbons and naphthenic hydrocarbons of nonhydroaromatic character having substantially equal boiling points, treating said separated fraction at a temperature below about 200 C. in the liquid phase under isomerization conditions with an aluminum chloride-hydrocarbon complex catalyst, and recovering cyclohexane from the isomerized distillate by fractional distillation.

2. A process for the production of methyl cyclohexane from naphthenic distillates which comprises the steps of separating from-a naphthenic distillate by fractional distillation a fracby fractional distillation a fraction boiling up to about 75-78 C.and containing parafiin hydrocarbons and naphthenic hydrocarbons of nonhydroaromatic character having substantially equal boiling points, treating said separated fraction at a temperature below about 200 C. in the liquid phase under isomerization conditions with an aluminum chloride isomerization catalyst, and recovering cyclohexane from the isomerized distillate by fractional distillation.

5. A process for the production of methyl cyclohexane from naphthenic distillates which comprises the steps of separating from a naphthenic distillate by fractional distillation a fraction boiling up to about 95-l00 C. and containing parafiin hydrocarbons and naphthenic hydrotion boiling up to about 95-100 C. and containing paraflin hydrocarbons and naphthenic hydrocarbons of'hon-hydroaromatic character having substantially equal boiling points, treating said separated fraction at a temperature below about 200 C. in the liquid phase under isomerization conditions with an aluminum chloride-hydrocarbon complex catalyst, and recovering methyl cyclohexane from the isomerized distillate by fractional distillation.

3. A process for the production of a hydroaromatic naphthene from a naphthenic distillate which comprises the steps of separating from a naphthenic distillate by fractional distillation a fraction boiling below about 150 C., and fraction boiling up to the boiling point of the hydroaromatic hydrocarbon which it is desired to produce and containing paraflin hydrocarbons and naphthenic hydrocarbons of non-hydroaromatic character having substantially equal boiling points, treating said separated fraction at a temperature below about 200 C. in the liquid phase under isomerization conditions with an aluminum chloride-hydrocarbon complex catalyst, and; re-

covering the hydroaromatic naphthene from the.

' isomerized distillate by fractional distillation.

carbons of non-hydroaromatic character having substantially equal boiling points, treating said separated fraction at a temperature below about 200 C. in the liquid phase under isomerization conditions with an aluminum chloride isomerization catalyst, and recovering methyl cyclohexane from the isomerized distillate by fractional distillation.

6. A process for the production of a hydroaromatic naphthene from a naphthenic distillate which comprises the steps of separating from a naphthenic distillate by fractional distillation a fraction boiling below about C., said fraction boiling up to the boiling point of the hydroaromatic hydrocarbon which it is desired to produce and containing parafiin hydrocarbons and naphthenic hydrocarbons of non-hydroaromatic character having substantially equal boiling points, treating said separated fraction at a temperature below about 200 C. in the liquid phase under the isomerization conditions with an aluminum chloride isomerization catalyst, and

recovering the hydroaromatic naphthene from the isomerized distillate by fractional distillation. 7. The process according to claim 6, in which the naphthenic hydrocarbon fraction subjected to the isomerization treatment is substantially 

